Production of resins



Patented-June 6, 1944 m'rso sTArss zsstnoo PRODUCTION OF RESINS,

Wilbert A. King, Memphis, Tenn., assignor, by mesne assignments, to Allied Chemical & Dye Corporation, a corporation of New York No Drawing. Application December 27, 1949,

Serial No. 372,008

7 Claims. (01. 260-32) This invention relates to a method of producing polystyrene resins and polymerized styrene homolog resins.

In the heat-polymerization of styrene or stytamination of the high-grade polymer with less valuable low-grade polymer.

It is an object of this invention to provide a method of effecting the removal of the monomer rene fractions at comparatively low temperatures, from a styrene compound polymer produced by say 75 to 125 C., a polymer is produced which when dissolved in toluene to form -25% (by weight) solution has a relatively high viscosity at C. The viscosity of the solution generally low-temperature polymerization of a styrene compound or fractions containing styrene compounds, which method does not result in the contamination of the high-grade polymer with less is recognized as an indication of the complexity ,lB valuable polymer and efiects in a simple and ecoof the polymer, the more viscous the solution the more complex the polymer, and for certain purposes, the better the resin. Heat-polymerization of styrene at higher temperatures yields a resin which when dissolved in toluene to form a 25% solution is substantially less viscous than the resinsolution formed by dissolving the resin produced by polymerizing styrene at the comparatively low temperatures mentioned.

nomical mannersubstantially complete removal of the monomer. Other objects and advantages of this invention will appear from the following detailed description thereof.

In accordance with this invention, styrene or v a styrene homolog, or fractions contang these substances, are heat-polymerized, preferably in a vessel provided with a reflux condenser to return evolved vapors-at temperatures tit. the range In heat-polymerizing styrene at the low tem- 25 of 75 to 125 C. to produce a high-grade polymer,

peratures mentioned it has not been found possible to polymerize the styrene substantially completely, even when using 100% styrene as the starting material, in a reasonable length of time.

and at the completion of the chosen polymerization period an organic solvent for the monomer and polymer having an initial boiling int somewhat above that of the monomer, for example,

Hence, some unpolymerized styrene invariably at least-about 5 above the boiling point of the not for the polymer. 'This precipitation method involves considerable time and difllculty to efiect -monomer, and not above about 225 'C., is then added to the polymer-monomer mixture and the resultant solution-distilled, either with live steam .or under reduced pressure or by passing an inert For example, it has been suggested to gas therethrough, i.- e. by employing low vaporpressure distillation, to elect removal of the :monomer and aportion of the solvent, a sumcient .quantity of the solvent being left in the mass to prevent the concentration of the polymer inthe separation and recovery of the polymer, and creasing toa p t where t p r above is, therefore; undesirable from a cost standpoint. It has also been proposed, particularlyin connection with the treatment of the polymer produced from 100% styreneas the-starting mate?- 125 C. would be necessary to maintain a suitably fluid co'nditionin the mass to eflect substantially complete removal pf the monomer. When the ,monomer has been substantially completely rerial, to elevate the temperature toward the-end-- 40 moved, t e es du Po t o of the solvent is (iii!- of the polymerization tothe point where poly-' y,

merization of themonomer'is substantially complete in a reasonable time. This has been-foundto result in undesirable formation of less complex .tilledofl. either by the use of live steam or under .low pressure, e. g. an absolute pressure of one inch of mercury.

Any organic solvent for the monomer and the polymers, even though the major portion of the polyme'r'having 8) boiling Po n Within the range monomer is converted to the polymerat comparatively low temperatureand the'polymerization temperature is raised only toward the. end of the operation. The use of steam or low-presfrom about 5 above the boiling point of the monomer "to about 225 0., preferably a solvent boiling from 15 C. to 25 6. above the monomer, which is inert relative to the monomer and polysure distillation has also been proposed for remover and does not fo m decompo t Products ing the monomer. This necessitates heating the mixture at temperatures substantially higher than those of the original polymerization, whereupon some polymerization of monomer occurs at these higher temperatures, resulting in con-. 35 benzenesboilingd t e r e o about 159 to or other reaction products under the conditions of operation which would contaminate the poly- 169 C., for use with styrene polymer-monomer mixtures, Hi-flash naphtha, i. e. distillate produced in the fractional distillation of coal tar and boiling within the range of about 150 C. to 225 C. for use with styrene compounds in general, which term is used herein to include styrene and styrene homologs, and durene, isodurene, tetralin, naphthalene or 1-ethyl-4-isobutyl benzene for use with polymer-monomer mixtures of styrene homologs. r

In operation it has been found that the process of this invention,- involving the polymerization of nearly all or at least a major portion of the styrene or styrene homol'og content of a styrene compound oil, followed by treatment as above described to remove monomer, results in substantially complete removal of the residual monomer without deieteriously aflecting the polymer. The presence of solvent in the monomer-polymer mixture facilitates the removal of the monomer by distillation under reduced pressure or with steam or inert gas at, temperatures not substantially above that of the polymerization temperature. Hence, if any polymerization does take Place at this low temperature, the polymer thus formed is of substantially the same grade as that produced in the polymerization operation and does not deleteriously affect the polymer ultimately recovered. After complete removal of the monomer, the high-grade polymer is left dissolved in a part of the added solvent. This solvent, as above noted, is not affected by higher temperatures, and thwe higher temperatures assasco a viscosity at C. of 950 centipoises when 25% by weight of resin was dissolved in toluene.

While the above example involves polymeriza-- mixture formed by polymerization of styrene or scribed above to remove monomer and solvent.

Since certain changes may be made in carrying out the above process without departing from necessary for the removal of the solvent, it has been found, do not aifect the qualityof the polymer.

The following example is illustrative of the process of this invention.

A drip-oil fraction containing by weight chiefly orthoxylene, was heated at C. for approximately forty hours. The partially polymerlzed material, a polymer-monomer-xylene solution, was then divided into two parts.

Part 1 was treated in accordance with this invention, namely, an equal amount of trimethyl of monomeric styrene, the remainder being distillate of substantially distilling from 160' C. to 169' C. W88

added thereto, the mixture was distilled in a column still maintained at 24 to 30 mm. of mercury absolute pressure \mtii the monomeric styrene had been completely removed as distillate, the still temperature remaining below 100' C. during this operation, and distillation discon tinued when the top of the column temperature corresponded to 160 C. at atmospheric pressure.

the scope of the invention, it is intended that all matter contained in the above description shall.-

illustrative and not in a limitmer-polymer mixture an organic solvent for the monuner and polymer having a boiling point above that of the monomer, which solvent is inert with respect to the polymer and upon subjecting to heat to eiiect separation thereof from the polymer does not react to form non-volatile residue or constituents deleteriously-aflectlng the polymer, and distilling the resultant mixture at a temperature not substantially above the polymerization temperature to remove as distillate from the mixture a suflicient portion of the added solvent to insure simultaneous removalas styrene present. I

2. A process of producing styrene polymer which comprises subjecting monomeric styrene to heat-polymerization at a temperature not ex ceeding C, until the major portion of the monomer has been polymerized, adding to the monomer-polymer mixture an organic solvent for the monomer-polymer boiling within the range of C. to 225 C., which solvent is inert with respect to the polymer. and upon subjection to'heat to effect separation thereof from the polymer does not react to form non-volatile residue or constituents deleteriously affecting the polymer,'.distilling the resultant mixture at a .0 temperature not exceeding 125' C. to remove as tion or live steam, the temperature of the bath was raised slowly so that at the endof three hours the temperature of the still contents was "220 '0. Live steam at approximately atmosresultant resin was removed and .found'to have distillate from the mixture a suilicient portion of the added solvent to insure simultaneous removal as distillate of substantially all the monomeric styrene present, 'and thereafter distilling the. residual solution to-eiiect removal of the remainder ofthe solvent. v

3. A process of producing styrene polymer which comprises subjecting to heat-polymerization a styrene monomer at a temperature not exceeding 125 C. until the major portion of the ,monomer has been polymerized, adding to the all the monomeric pound polymer by subjecting monomeric styrene tion substantially all the monomeric styrene present and a portion of the trimethyl benzene, and thereafter distilling the residual solution to effect removal of the remainder of the trlmethyl benzene.

a. A process of producing styrene polymer which comprises subjecting to heat-polymerization monomeric styrene at a temperature not exceeding 125 C. until the major portion of the monomer has been polymerized, adding to the monomer-polymer mixture a Hi-flash naphtha boiling within the range of 150 C. to 225 C., subjecting the resultant solution to low vapor pressure distillation at a temperature not exceed-- ing 125 C. to remove as distillate from said solution substantially all monomeric styrene present and a portion of the solvent, and thereafter distilling the residual solution to effect removal I of the remainder of the solvent.

5. A process for the production of polymerized styrene which comprises subjecting monomeric styrene to heat-polymerization at a temperature not exceeding 125 C. until the major portion of the monomer has been polymerized, adding to the monomer-polymer mixture an organic solvent for the monomer and polymer bofling within the range of about 159 C. to 169 C., which sol-' vent is inert with respect to monomer and polymer and which solvent upon subjection to heat to effect separation thereot from the polymer will not react to form non-volatile residue or constituents deleteriously affecting the polymer, subcompound to polymerization at a temperature not exceeding 125 C. to produce a high-grade polymer containing a minor proportion of monomer, and thereafter distilling to effect removal of the monomer from the polymer, the improvement which comprises carrying out the distillation to remove monomer at a temperature not substantially above the polymerization temperature in the presence of an organic solvent for the monomer and polymer, which solvent has a boiling point substantially above that of the monomer, is inert with respect to the polymer and upon subjection to heat to eflect separation thereof from the polymer does not react to form non-volatile residue or constituents deleteriously aiiecting the polymer, and continuing said distillation, vaporizing said solvent together with monomeric styrene compound, until substantially complete removal of said monomer and a portion of said solvent, as distillate, has been eflected.

7. A process for producing a styrene compound polymer which comprises subjecting monomeric styrene compound to polymerization at a temperature not exceeding 125 C. until the major portion of the monomer has been polymerized, adding to the monomer-polymer mixture an organic solvent for the monomer and polymer having a boiling point above that of the monomer, which solvent is inert with respect to the polymer and-upon subjecting to heat to effect separation thereof from the polymer does not react to form non-volatile residue or constituents deleteriously afiecting the polymer, and distilling the resultant mixture at a temperature not substantially above the polymerization temperature to remove as distillate from the mixture 9. sufllcient portion of the added solvent to insure simultaneous removal as distillate of substantially all the monomeric styrene compound present.

' WIIBERT A. KING. 

